On April through August 1790, M.S. Novikov, counselor of the Russian embassy in The Hague, stayed by order of S.A. Kolytchev, Russian minister plenipotentiary in the Dutch Republic, for a «secret mission» in the Belgian revolutionary republic. The paper’s purpose is to consider the features of the Russian spy mission’s preparations, as well as his strategies during his stay in Belgium. Due to his contacts with Belgian royalists, M.S. Novikov could gather information on the state of affairs in the republican army and in the revolutionary government, as well as on its contacts with foreign courts.